Microelectronics Packaging for Medical Implants - Crane Electronics.pdf · Ref. Medical Device Today, April 2010 7 . Cochlear implants are surgically implanted devices for individuals

Microelectronics Packaging

for

Medical Implants

Presented by:

Faina Zaslavsky

History and background - hybrid microcircuits

Shortly after the development of practical transistors in the mid-

1950s, the U.S. Army Signal Corps and RCA developed hybrid

microcircuits as dense assemblies of transistors and other

components.

Hybrid circuits comprise one or more transistor chips and passive

components like resistors and capacitors mounted on a ceramic

substrate and interconnected with wires and conductive traces.

Ref. Computer History Museum, The Silicon Engine

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In 1965, Intel co-founder Gordon Moore predicted exponential

growth in the number of transistors incorporated on a single chip.

As "Moore's Law" became widely known, it became a self-

fulfilling prophecy that emerged as one of the driving principles

of the semiconductor industry.

Since Moore's prediction, IC transistor counts have doubled

every two years, allowing ever increasingly complex functions to

be integrated on a single chip.

Ref. Computer History Museum, The Silicon Engine

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The complexity of functions implemented in hybrid circuits

has increased in parallel with the complexity of integrated

circuits.

Early hand crafted hybrid circuits were labor intensive and

expensive to produce.

Multichip modules (MCM) and packages (MCP) are modern

machine assembled hybrids used in high performance, high

volume applications like automotive controls, cell phones and

wireless networks.

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Early hybrids used simple ceramic substrates with a single layer

of metal interconnection on the surface.

The simple hybrid substrate evolved into high temperature co-

fired ceramic (HTCC) substrates incorporating many layers of

circuitry, fused together at 1600°C.

With the addition of soldered or otherwise attached ring frame

and the metal lids, the HTCC substrates became complete

packages incorporating complex functions.


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HTCC packages became a platform for many medical implants


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Application background - Cochlear Implants

Hearing loss is one of the most common sensory impairments and affects 28 million Americans.

Approximately 1-3 out of 1,000 newborns has impaired hearing.

The elderly are more commonly affected with 40-50% of people over age 75 having hearing loss.

Depending on the degree of hearing loss, many affected individuals can be successfully fitted with hearing aids that amplify sound.

For patients with hearing loss that is not mitigated with hearing aids, a cochlear implant may provide an opportunity for hearing.

Ref. Medical Device Today, April 2010

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Cochlear implants are surgically implanted devices for

individuals with severe to profound hearing loss who only receive

limited benefit from amplification with hearing aids.

A cochlear implant provides direct electrical stimulation to the

auditory nerve via electrodes, bypassing the usual transducer

cells that are absent or nonfunctional in deaf cochlea.

As of 2005, an estimated 85,000 patients worldwide have

received cochlear implants. However, this number represents

only a small number of the estimated 250,000 hearing-

impaired individuals who may benefit from a cochlear implant.


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Although individual responses to cochlear implants are highly

variable and depend on a number of physical and psychosocial

factors, the trend toward improved performance with

increasingly sophisticated electrodes and programming

strategies has dramatically expanded indications for cochlear

implantation.

Ref. Medical Device Today, April 2010


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Throughout the 1970s, the Food and Drug Administration (FDA)

recommended that devices be implanted only in adults with

profound hearing loss.

Over time, indications have been broadened to include adults

with severe hearing loss who may achieve some benefit from

conventional amplification (hearing aids).

In 1980, the FDA allowed children at least 2 years of age to be

implanted.

The age limit has recently been lowered to 12 months for all 3

devices available in the United States (Advanced Bionics, Med-

El, and Cochlear Corporation devices).


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Cochlear Implants

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Cochlear implants consist of both an externally worn component

and an internally implanted component.

The external component includes a microphone, an external

sound processor, and an external transmitter.

The internal component is surgically implanted and includes an

internal receiver placed within the temporal bone and an

electrode array that extends from the receiver into the cochlea

through a surgically created opening in the round window of the

middle ear.

Cochlear Implants

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Sounds that are picked up by the microphone are carried to the

external sound processor, which transforms sound into coded

signals that are then transmitted transcutaneously to the

implanted internal receiver.

The receiver converts the incoming signals to electrical

impulses that are then conveyed to the electrode array,

ultimately stimulating the auditory nerve.

Cochlear Implants

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Several cochlear implants are commercially available in the U.S.:

the Nucleus family of devices, manufactured by Cochlear

Corporation; the Clarion family of devices, manufactured by

Advanced Bionics and the Combi 40+ device, manufactured by

Med El Corporation.

Over the years, subsequent generations of the various

components of the devices have been approved by the U.S.

Food and Drug Administration (FDA), focusing on improved

electrode design and speech-processing capabilities.

Cochlear Implants

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Furthermore, smaller devices and the accumulating experience in

children have resulted in broadening of the selection criteria to

include children as young as 12 months.

The first cochlear implant electronics were produced on HTCC

substrates with hermetically sealed cavities. Enclosed in the

cavity were ASICs (application-specific integrated circuits) with

supporting active circuitry. Passive components were mounted

external to the cavity.

Cochlear Implants

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The microelectronics circuit was assembled, electrically tested

and environmentally screened to the prescribed customer

specification.

The assembly and screening sequence was based on the MIL-

PRF-38534 specification that establishes the general

performance requirements for hybrid microcircuits, Multi-Chip

Modules (MCM) and similar devices, along with the verification

and validation requirements for ensuring that these devices

meet the applicable performance requirements.

Cochlear Implants

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Placing the devices in children as young as 12 months old required lighter and smaller implants.

The second generation of the implant electronics was assembled on green organic board with ASICs configured into CSPs (chip scale packages).

The changes in the configuration and assembly techniques allowed for the additional weight and size reduction without compromising device reliability.

Cochlear Implants

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Cochlear Implants

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The CSPs were produced as sub-assemblies using known

good dice (KGD) and connectivity was validated via in-line X-

ray.

To add more functionality while further reducing size and weight

of the micro-circuit, the latest implant generation uses CSP

ASICs mounted on hard-flex substrates.

This assembly configuration presents unique challenges,

requiring specialty fixturing throughout the assembly process as

well as electrical testing and environmental screening. The end

result is a robust and reliable product suitable for long term

medical implant.

Cochlear Implants

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Future challenges for medical implants

The market for neurostimulation products in the US was valued

at approximately $1.3 billion in 2009 and it has not yet

scratched the surface of its potential.

According to "US Markets for Neurostimulation Products," a

report published in March by the Medtech Insight division of

Elsevier Business Intelligence, this market is projected to grow

at a healthy compound annual rate of almost 16%, reaching

more than $2.7 billion five years from now.

Ref. BCC Research, Market Forecasting, May 2011

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There are three main modalities of implantable

neurostimulation therapy — vagus nerve stimulation (VNS),

spinal cord stimulation (SCS), and deep brain stimulation

(DBS).


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Each therapy modality poses a different challenge and requires a

different technology. The common factors among all of

neurostimulators will be ever smaller footprint, higher density and

tighter spacing of the components.

Medical Implants

Takeaways:

The common factor among all medical implants – small size, light

weight, high reliability

Continuous size reductions made possible through innovative

miniaturization techniques

Emerging neurostimulation VNS and DBS devices will require

further developments in materials and implant configurations

Maintaining High reliability, while reducing Size, Weight and Cost

of the implants are key focus for the future

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Thank you

Faina Zaslavsky Director, Microelectronics Solutions

Business Unit

Crane Electronics, Inc.

Phone: (425) 895-5079

[email protected]

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Documents

Microelectronics Packaging for Medical Implants - Crane Electronics.pdf · Ref. Medical Device Today, April 2010 7 . Cochlear implants are surgically implanted devices for individuals